Semiconductor memory devices have continued to have increased memory capacity, decreased access times, and greater functionality over their predecessors. However, as a result of designing memory devices having higher capacity, higher speed, and greater functionality, current memory devices typically consume more power than their predecessors during normal operation. Additionally, the number of inputs, or correspondingly, the number of signals that need to be provided to a memory device for normal operation has increased significantly.
Although power consumption has been in the past of some concern, it has more recently become an issue of much greater significance. There are many reasons for wanting to design more power efficient memory devices. One such reason is that many applications in which current memory devices are used are for portable applications, which typically means that power is supplied by batteries, or other lightweight and fixed capacity power supplies. Generally speaking, consumers find it undesirable to replace batteries, or be forced to recharge batteries often. Consequently, memory device manufacturers have made an effort in designing more power efficient memory devices. Whatever the particular reason, the issue of the increased power consumption of current memory devices cannot be ignored.
With respect to the number of pins or inputs on a memory device, it is often undesirable to have a memory device with many pins. That is, more leads often means that more signals need to be provided. As a result, signal drivers, controllers, and circuit boards need to be more complex. Additionally, more leads also often means larger memory devices, or if not larger, then a memory device is very narrow pitch between leads. Neither one of these situations is looked upon as desirable.
Many different approaches have been taken to address the issue of increased power consumption of current memory devices. For example, one straight forward approach has been to use higher capacity batteries that can provide higher power over a greater period of time before the need for recharging or replacement. However, these higher capacity batteries are generally more expensive, and are often larger and heavier. Also, as previously discussed, consumers dislike the inconvenience of changing batteries or charging rechargeable batteries often. Moreover, the approach fails to directly address the issue of power consumption by memory devices.
Other approaches have been directed to designing more power efficient memory devices, for example, designing more sophisticated internal voltage regulators and internal power supplies so that relatively less power is consumed during operation of the memory device. These types of approaches are often desirable, since many of the different designs, which may not save a significant amount of power by themselves, can be incorporated together in a memory device such that the cumulative power savings are significant. Therefore, there is a need for additional approaches to designing efficient, lower-power consuming memory devices.